The present invention relates to an electric supply and heat radiating apparatus for a power semiconductor device in an electric circuit having a plurality of power semiconductor devices, wherein the power semiconductor devices are made to have a simplified electric supply structure and a heat radiation action.
Generally, a control device to which a relatively large power is supplied has an electric circuit provided with a plurality of power semiconductor devices. For example, for the electric vehicle receiving attention these days, an electric motor as a vehicle drive source and its motor drive circuit, namely a device having a plurality of power semiconductor devices, are housed in a metallic casing to protect the motor and the circuit and mounted on the vehicle. This casing comprises a metallic cylindrical case and cover made of aluminum or the like and is assembled by housing the motor section in the case, placing the cover in position and joining the case and the cover with bolts.
The motor drive circuit mainly comprises power semiconductor devices as the switching device for controlling switching the electric supply to the motor coil at a high speed. And, when the power semiconductor devices generate heat up to a rated temperature, it is necessary to suppress or stop the output of the motor in order to protect the circuit. Then, in order to avoid occurrence of such a situation and to obtain a high power, it is inevitable to externally release the heat of the power semiconductor devices to out of the motor case.
Therefore, conventionally, the heat radiation metallic parts provided on the power semiconductor devices are mounted on a heat sink having a heat radiating action.
In such a conventional electric circuit, e.g., FET, the drain electrode and the heat radiation metallic part of the power semiconductor device are electrically connected. And when a power semiconductor device used on a different circuit section is mounted on the same heat sink, it is necessary to electrically insulate the respective power semiconductor devices from the heat sink.
And, when the electrical insulation is secured as described above, the heat radiation property of the power semiconductor device is degraded because when the electrical insulator has a high electric resistance, it also has a high heat resistance.
When the power semiconductor device is soldered to a circuit board to provide a circuit structure, the circuit is generally connected to terminals on the circuit board for connecting to an external circuit such as a power supply and a motor. But, the power semiconductor device generally deals with a large current and requires, for example, a structure or a process for forming a pattern with copper foils having a large thickness on the circuit board, to form the circuit board in a multilayered structure to use its inner layer or to form a grommet terminal on the circuit board. Therefore, the conventional circuit board has a complex structure which is hard to be made small, and needs many parts and processes, resulting in a high cost.
In view of the aforesaid problems, it is an object of the invention to provide an electric supply and heat radiating apparatus for a power semiconductor device which is mounted on a circuit board, has a simplified electric supply structure for the power semiconductor device and also a heat radiation action.
According to an aspect of the invention, an electric supply and heat radiating apparatus for a power semiconductor device in an electric circuit using a plurality of power semiconductor devices is characterized in that:
the power semiconductor devices are provided with heat radiation metallic parts to which electrodes of the devices are electrically connected within packages of the semiconductors;
among the plurality of power semiconductor devices, the heat radiation metallic parts of those having the electrodes of the same potential connected to the heat radiation metallic parts are electrically connected and secured to a single radiator having conductivity; and
the radiator is used as one connection terminal.
As described above, according to the apparatus of the invention, the plurality of heat radiation metallic parts are electrically connected to the single radiator, which is used as the single connection terminal. Accordingly, the necessity of separate wiring from the electrodes related to the plurality of heat radiation metallic parts can be eliminated, and the electric supply structure can be simplified.
Besides, the plurality of heat radiation metallic parts are connected to the radiator without through an electric insulator, so that a heat resistance between the individual power semiconductor devices and the radiator can be made small, and the heat radiation of the power semiconductor devices can be enhanced.
The radiator is provided in a plurality of numbers and electrically connected and fixed to a single conductive heat radiating plate, and the heat radiating plate is used as one connection terminal.
Thus, the plurality of radiators are electrically connected to the heat radiating plate so to be used as a single connection terminal, so that the aforesaid electric supply structure can be made more simple. Since the plurality of radiators are additionally connected to the heat radiating plate, the heat radiation property of the power semiconductor devices can be enhanced further more.
The heat radiating plate is electrically insulated and fixed to another radiator.
In the aforesaid structure, heat of the heat radiating plate is released by another radiator, so that the heat radiation property of the power semiconductor devices can be improved further more.
The radiator is electrically insulated and fixed to another radiator.
In the aforesaid structure, heat of the radiator is released by another radiator, so that the heat radiation property of the power semiconductor devices can be improved further more.
Fixing areas between the radiator and another radiator are larger than the fixing areas between the radiator and the heat radiation metallic parts.
The aforesaid structure further improves the heat radiation property of the power semiconductor devices.
Specifically, when the radiator and another radiator are electrically insulated, a heat resistance between them is increased, but the present invention has determined the fixing areas between the radiator and another radiator to be larger than those between the radiator and the heat radiation metallic parts. Therefore, an mount of heat conducted from the heat radiation metallic parts to the radiator and an amount of heat conducted from the radiator to another radiator can be secured in good balance. As a result, heat of the power semiconductor devices can be radiated efficiently.
The radiator is a plate member and secured to another radiator by screws.
By configuring as described above, the radiator can be provided efficiently.
Especially, the radiator of the present invention is a plate member and can be produced by stamping, and its production cost can be reduced.